A piezoelectric resonator unit is an example of a piezoelectric device that is used as an oscillation device, a band-pass filter, or the like. A quartz crystal resonator unit, which is an example of a piezoelectric resonator unit, includes a quartz crystal resonator and an enclosure that holds the quartz crystal resonator. The enclosure includes a substrate, on which the quartz crystal resonator is mounted, and a cap (metal cover) that is joined to the substrate via a sealing material. Such a quartz crystal resonator unit is known as an example of a piezoelectric device that is used as an oscillation device, a band-pass filter, or the like (see, for example, Patent Document 1). The cap is open toward the substrate, and, by joining the cap to the substrate via the sealing material, the piezoelectric resonator can be hermetically sealed in the enclosure.
However, with such a structure, the mounting position of the piezoelectric resonator may vary, since an upper surface of the substrate (a surface on which the piezoelectric resonator is mounted) is flat and does not have a guide portion for positioning the piezoelectric resonator. Moreover, when joining the cap to the substrate, the joining position of the cap may vary, and thus the cap may be joined to the substrate in a state in which the cap is in contact with the piezoelectric resonator on the substrate.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2012-191648